The head of Ukraine's National Security Council has said Kyiv is open to placing parts of a missile-defense system on Ukrainian soil to ward off the potential risk of attacks from Russia.

Oleksandr Turchynov told the Ukrinform news agency on May 20: "I do not rule out that to defend ourselves from [Russia's] nuclear threat, we will have to hold consultations on deploying components of a missile-defense system on Ukrainian territory."

In Moscow, Kremlin spokesman Dmitry Peskov said Russia would consider the deployment of such components to Ukraine "a threat to Russia's security."

"This will entail the need for taking retaliatory measures," he added.

Moscow has strongly criticized plans to build a U.S.-led missile shield in Europe, which NATO says is not directed against Russia but rather an attack from a country like Iran.